Iran is reported to be using two main mine types in the Strait of Hormuz: a buoyant, moored mine and a bottom mine. Open-source reporting identifies them as the Maham-3 and Maham-7.maritime-executive+1
The Maham-3 is described as a moored, buoyant mine that floats below the surface and uses acoustic sensors to detect nearby ships. The Maham-7 is described as a bottom mine that can be laid in shallow water and is meant to threaten smaller vessels as well as patrol craft.maritime-executive
Moored mines are dangerous because they sit at a set depth and can detonate when a ship passes close enough or triggers their sensors. Bottom mines are harder to notice because they rest on the seabed and can be placed in shallow channels where ships may still need to travel.maritime-executive+1
Other reporting also notes that Iran has a large stockpile of naval mines and a mix of older and newer designs, including drifting mines in general discussions of Iranian mine warfare. In the Strait of Hormuz, the practical threat comes less from any single mine and more from the combination of narrow waters, hidden placement, and the difficulty of clearance.cbc+2
If you want, I can make a simple table comparing moored, drifting, and bottom mines.